Yin and Yang Dual Characters of CuO_x Clusters for C–C Bond Oxidation Driven by Visible Light

Abstract

Selective cleavage of C-C bond is pursued as a useful chemical transformation method in biomass utilization. Herein, we report a hybrid CuO x /ceria/anatase nanotubes catalyst in the selective oxidation of C-C bond under visible light irradiation. Using lignin β-1 model as substrate offers 96% yields of benzaldehydes.Characterized results by high angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) and energy-dispersive X-ray spectroscopy-element

Catalytic Scissoring of Lignin into Aryl Monomers

“…Consequently, the C α C β bond was cleaved to produce aldehydes. Wang and co‐workers prepared a hybrid CuO x /ceria/anatase nanotube (CuOx/ceria/A‐NTs) catalyst for the oxidative cleavage of β‐1 models to produce aromatic aldehydes under visible‐light irradiation . CuOx and ceria nanoparticles were homogeneously located on the anatase nanotube ( Figure ).…”

“…d) A high‐resolution HAADF STEM image of CuOx/ceria/A‐NTs and the corresponding EDX maps (e−i). Reproduced with permission . Copyright 2017, American Chemical Society.…”

Conversion of Lignin Models by Photoredox Catalysis

“…Wang and co-workers synthesized aC uO x /ceria/anatase composite as ah eterogeneousp hotocatalyst to promote CÀCb ond cleavage in b-1 models with 98 %s electivity( Scheme 11). [52] Under visible-light irradiation (l = 455 nm), the highly dispersed CuO x clusters exhibited bifunctionality towardC ÀCb ond photolysis. On the one hand, CuO x on ceria promotes the efficiency of CÀCb ond cleavage by increasing the surfaceo xygen vacanciesa nd the Ce 3 + ions that are closely associated with its photocatalytic performance.…”

Redox-neutral photocatalytic strategy for selective C–C bond cleavage of lignin and lignin models via PCET process

“…It is known that C-C bond cleavage of b-1 model is more efficient than that of b-O-4 model [55]. Many advancements have been achieved in the selective C-C bond cleavage of b-1 models [25,56,57]. Success achieved in the selective C a -C b bond cleavage in b-O-4 lignin models promoted us to apply this facile visiblelight driven photocatalytic strategy to the degradation of b-1 lignin model, 1-(4-methoxyphenyl)-2-phenylethan-1-ol (P) with a a-OH group.…”

“…Activation of the primary alcohol by Cp*Ir-bypyridonate catalyst enabled the C a -C b bond cleavage of lignin at 130°C, affording a range of non-phenolic monomers (Scheme 1b) [19]. Recently, some advancements have been achieved in the application of photochemical strategy to the depolymerization of lignin under mild conditions [9,[20][21][22][23][24][25]. Wang and co-workers [24] reported a photocatalytic oxidative strategy for C-C bond cleavage along with C b -O bond cleavage in lignin b-O-4 linkages using a mesoporous graphitic carbon nitride catalyst (mpg-C 3 N 4 ), furnishing 4-methoxybenzaldehyde, 4-methoxybenzoic acid and 2methoxyphenol in 36%, 37% and 22% yield, respectively (Scheme 1c).…”